__qualname__ (PEP-3155)

In Python 3.3, PEP-3155 introduced a new __qualname__ attribute for classes and functions which contains a full dotted path to the definition of the given object.

class A:
  class B:
    def f(self):
      def g():
        pass
      return g

A.B.f.__name__
# 'f'

A.B.f.__qualname__
# 'A.B.f'

g = A.B().f()
g.__name__
# 'g'

g.__qualname__
# 'A.B.f.<locals>.g'